Some Minnesota physicians returning from the American Heart Association meeting in Dallas say they will stick with old guidelines for determining when to use cholesterol-lowering drugs, or statins, until the validity of a new risk calculator is verified. The calculator, released Nov. 12 by the Heart Association and the American College of Cardiology, is designed to estimate a patient's risk of having a heart attack or stroke over the next 10 years. But after testing the calculator, several prominent cardiologists and researchers found that it vastly overestimates the number of patients who need statin therapy.